In European Patent 170006, there are disclosed a series of compounds identified as LL-F28249. Of the 14 compounds disclosed, 13 have a milbemycin type macrocyclic ring system with a branched unsaturated alkyl side chain of from 4 to 7 carbon atoms at the 25-position. The compounds are best described in the following structural formulae: ##STR1##
__________________________________________________________________________ Component R.sub.1 R.sub.2 R.sub.3 R.sub.4 R.sub.5 R.sub.6 R.sub.5 + R.sub.6 A-B B-C __________________________________________________________________________ LL-F28249a CH(CH.sub.3).sub.2 H CH.sub.3 CH.sub.3 --O--CH.sub.2 -- CH--CH CH.dbd.C LL-F28249B CH.sub.3 H CH.sub.3 CH.sub.3 --O--CH.sub.2 -- CH--CH CH.dbd.C LL-F28249Y CH.sub.3 CH.sub.3 CH.sub.3 CH.sub.3 --O--CH.sub.2 -- CH--CH CH.dbd.C LL-F28249w CH.sub.3 CH.sub.3 CH.sub.3 CH.sub.3 OH CH.sub.2 OH CH--CH CH.dbd.C LL-F28249e CH(CH.sub.3).sub.2 H H CH.sub.3 --O--CH.sub.2 -- CH--CH CH.dbd.C LL-F28249z CH.sub.2 CH.sub.3 H CH.sub.3 CH.sub.3 --O--CH.sub.2 -- CH--CH CH.dbd.C LL-F28249h CH(CH.sub.3).sub.2 H CH.sub.3 CH.sub.3 --O--CH.sub.2 -- C.dbd.CH CH--CH LL-F28249r CH(CH.sub.3).sub.2 H CH.sub.3 CH.sub.2 CH.sub.3 --O--CH.sub.2 -- CH--CH CH.dbd.C LL-F28249i CH(CH.sub.3).sub.2 H CH.sub.2 CH.sub.3 CH.sub.3 --O--CH.sub.2 -- CH--CH CH.dbd.C LL-F28249k CH.sub.3 CH.sub.3 CH.sub.3 CH.sub.3 H CH.sub.3 CH--CH CH.dbd.C LL-F28249g CH(CH.sub.3).sub.2 CH.sub.3 CH.sub.3 CH.sub.3 --O--CH.sub.2 -- CH--CH CH.dbd.C LL-F28249m CH(CH.sub.3).sub.2 CH.sub.3 CH.sub.3 CH.sub.3 H CH.sub.3 CH--CH CH.dbd.C __________________________________________________________________________ ##STR2##
The LL-F28249 compounds are prepared by the fermentation of Streptomyces cyaneogriseus sub sp. noncyanogenous NRRL15773. The morphological characteristics of NRRL15773 are completely described in the above-cited European patent along with processes for the preparation of such compounds.